Nutrient (e.g., nitrogen and phosphorus) pollution in water bodies (e.g., rivers, streams, lakes, ponds, reservoirs, retention ponds) is a major pollution problem. Nutrients may run off farmland and other fields (e.g., grazing), land inhabited by wildlife, and even land in urban areas (e.g., where lawn fertilizers are used or pet waste is left). These nutrients may cause high levels of algae and other plant growth. This growth takes oxygen and sunlight out of the ecosystem. The water then becomes unsafe for humans and animals and causes so-called “dead” zones where fish cannot survive.